purchased new electric dryer,new cord is a 4 wire.old dryer had 3 wire.(220V)Purchased a 4wire receptacle,but when I removed old receptacle from the wall(3wire)(wired with romex in wall in laundry room,good 50' from panel and walls all finished)I found only 3 wires and the wall box is plastic.(no mech ground grn available)apears to be a #10 2 wire with ground which apears to be #12 wire. Why the change from 3wire to 4wire and if I put the wires back just as before using 4wire cord but doubling white & grn together whats the harm?(jumper) My electric stove wired the same way I took it apart????Both wires end up on same terminal block back at breaker panel anyway if they were a 4wire romex.Question why the change and whats reasoning safety factor, has to be millions still connected with a 3 wire connection.Good ? for DON K. Can you help me with this. TY also aware that a 10/3W grnd should have been used when originally wired as your not supposed to derate neutral, on a dryer cir if I remember right,especially if pipe used. TY again

Hi eagle, wonder why Don hasn't picked this up yet, here's a answer the way I see it.

The newer 220 volt dryers and stoves have added the neutrel (white)
wire to take care of the 120 volt accessories that may be
installed in these appliances. eg light, timer motors etc.
The older units used the ground conductor for this which presented a very dangerous condition if the grounding
was interupted anywhere in the home.

My advice would be to get a grounding (green) conductor to the new
4 prong recept. You could do this by running a seperate #12 green wire from
the ground lug on the recpt. to the nearest COLD water pipe &
connected with an approved ground clamp.

Then make sure that the neutrel wire in the romax is connected to
neutrel buss in the panel.

This is a prime example of why I dislike Romax. Any addition
or upgrade to your system is made so much more difficult.

If this was in conduit it would have been a simple matter
to pull in the additional required conductor.

Hope Don adds to this, as his explanations are much better then mine.

Regards Mike b. (AKA Byter)

Byter:

The White neutral wire was always one of the three wires in the cable along with two blacks or one black & one red wire, all AWG No.10 copper.

It is the AWG No.10 Green ground wire that has been added.

Byter & Eagle:

To my knowledge the only thing that the plug on the dryer & the receptacle in the cable going back to the Power Panel added was the green AWG No.10 ground wire.

To my knowledge, I have NOT found anything specific in the 2002 NEC Code referring to the new four wire connection.

I have found data in Handymanwire Expert Forums showing the three & four wire connectors. This is the URL:

http://www.handymanwire.com/
cgi-bin/handymanwire/ubb/ultimatebb.cgi?ubb=
get topic&f=2&t=001356

In the old three wire setup, the white neutral served as the return & the equipment ground. This is no longer the case.

In the new setup, I do not know whether the dryer is using the white or green wire for the return of the 220-volt circuit or for other returns for dryer lights or any other circuit using 120-volts.

It would be my opinion that the return for any 120-volt circuit would be the White Neutral.

That way the only time that the green wire would carry current is if there is a malfunction in the dryer or a short.

Eagle:

You can connect up your dryer with only three wires using your existing cable. Just be sure that you connect the black wire to the 'X' connector, the red wire to the 'Y' connector & the White wire to the 'N' connector in the old Plug.

Run an AWG No.10 bare copper wire from the frame of the dryer to the cold water line in your washroom with a suitable copper clamp. That will serve the same purpose as the green wire that would normally be connected from the 'G' terminal of the plug via the four wire receptacle back to the power panel.

If you decide to leave the four wire plug on the dryer please find a way to run a separate AWG No. 10 green wire from the receptacle back to the power panel. Connect it to the 'G' terminal on the four wire receptacle & the grounding Bussbar in the Power Panel.

You can run this wire through wire mold on the outside surface of you wall up into the ceiling. Somehow you ought to be able to fish it from there to your Power Panel without tearing up too much of your finished basement.

[This message was edited by donaldekliros on 08-30-02 at 06:17 PM.]